feat: Add support for setting values of different type but same kind

The canonical case here is different string types: eg a password field
that has custom formatting methods for redacting values.

Author: wdullaer

env_test.go

@@ -100,6 +100,7 @@ func setEnvVars(t *testing.T, structName, prefix string) {
 			"EPOCH":                      "1638551008",
 			"EPOCH32":                    "1638551009",
 			"EPOCH64":                    "1638551010",
+			"ROOTPASSWORD":               "mystery",
 		}
 	case "CamelCaseServer":
 		env = map[string]string{

flag_test.go

@@ -284,6 +284,7 @@ func getFlags(t *testing.T, structName, prefix string) []string {
 			"-epoch":                      "1638551008",
 			"-epoch32":                    "1638551009",
 			"-epoch64":                    "1638551010",
+			"-rootpassword":               "mystery",
 		}
 	case "FlattenedServer":
 		flags = map[string]string{